1. Field of the Invention
The present invention concerns a method for purging a high purity manifold, and, more particularly, a method for purging that comprises the injection of a purge gas into the manifold while vacuum is applied to the manifold.
2. Description of Related Art
High purity chemical delivery systems typically comprise manifolds that include diaphragm valves connected by conduits and connectors that connect the manifold to adjoining equipment.
For instance, in the semiconductor industry, high purity chemicals such as tetrakis (dymethilamino) titanium (TDMAT), tetrakis (diethylamino) titanium (TDEAT), tantalum pentaethoxide (TAETO), copper hexafluoroacetylacetonate-trimethylvinylsilane (Cu(hfac)TMVS), tetramethyltetracyclosiloxane (TMCTS), tetraethyl ortosilicate (TEOS), and trimethylphosphate (TMP) are delivered from a primary storage container to a process tool or to a secondary storage container by means of manifolds that regulate the flow of the high purity chemical during ordinary process conditions, and that also regulate the flow of pressurized gases and of vacuum during purge cycles.
When a storage container has exhausted the supply of high purity chemical and must be replaced, the manifolds connected to the container must be thoroughly purged prior to and after the installation of the new container, in order to remove any impurities and any ambient gases that may have entered the system during the container replacement process. Purge cycles must also be performed when a storage container is refilled rather than replaced, and when a component attached to the manifold (for instance, a flow controller) is replaced. Due to the high purity levels required, these purge cycles are extremely time consuming and generate an increase in manufacturing costs due to the related manufacturing down-times, to the large amounts of purge gas required, and to the increased wear on the filter systems installed in the plant.
Such high purity manifolds are designed to transport the chemical with a laminar flow. Consequently, the removal during the purge cycle of any chemical residuals that may be still attached to the inner walls of the manifold is a highly inefficient process, as the velocity of the purge gas in the proximity of the manifold walls approaches zero under laminar flow conditions, thus creating points of stagnation. Therefore, the purge cycles in the prior art perform no effective removal of such chemical residuals.
Therefore, there is a need for a method for purging a manifold for the delivery of a high purity chemical that minimizes purge times and material consumptions.
There is a further need for a method for purging a manifold for the delivery of a high purity chemical that achieves a turbulent flow of the purge gas within the manifold without creating points of stagnation, thereby increasing the rate of removal of the high purity chemical that is attached to the inner walls of the manifold.